One of the main roles of the taste system is to identify nutrients an organism needs to survive. Historically, the taste system has been thought of as inflexible, merely reporting the presence of taste stimuli. However, recent evidence suggests that the taste system may be modulated by a number of hormones that may alter the expression and/or function of elements involved in nutrient taste transduction. The primary goal of the proposed studies is to explore the ability of the taste system to respond to regulatory cues, like hormones, that may modulate the peripheral gustatory system by acting on specific transduction elements. One goal of the project is to further identify channels that participate in salt and water transduction in rat taste cells. The first aim of the project will test the hyposthesis that many of the same ion channels and water channels that are expressed in other salt and water transporting epithelia are also expressed in the peripheral gustatory system. Molecular biological, immunocytochemical and electrophysiological techniques will be used to determine the expression and function of channels that may play roles in both salt and water transduction pathways. These include identification and characterization of the epithelial sodium channel (ENaC) involved in sodium salt taste, the chloride channels of the CIC family and the cystic fibrosis transmembrane conductance regulator (CFTR), aquaporin (AQP) water channels, the inward rectifying potassium channel, ROMK1, all that shown to be present in mammalian taste cells by preliminary data. The second goal of the proposed research will investigate the ability of several natriferic hormones (aldosterone, vasopressin and atrial natriuretic peptide) to modulate expression and function of these identified elements. A common feature of the aforementioned channels is that they are regulated by one or more of these hormones that maintain help salt and water balance in transporting epithelia. We will test the hypothesis that the transduction elements that contribute to salt and water transport in taste cells respond to one or more of the natriferic hormones that regulate salt and water movement in other epithelia. Using quantitative real-time PCR and electrophysiological recording in rat taste cells we will examine the ability of these three hormones to alter the relative expression and function of ENaC, CIC, CFTR, AQP and ROMK1. Taken together, these studies should help to further elucidate the transduction pathways for salts and water in mammalian taste cells. In addition, it should provide some of the first direct evidence as to the ability of specific elements in taste transduction pathways to be modulated by hormonal signals and to identify the mechanism underlying such modulation. These studies will attempt to provide direct evidence that the gustatory system is flexible and that it plays an active role in helping maintain and restore nutrient balance. [unreadable] [unreadable]